How can I tell if my vehicle has an antitheft system install from the factory? I have keyless entry, but how else can I tell if there is a starter kill or anything of that nature?

Your truck is equipped with the PASSLOCK system which has both Vehicle theft deterrent and Content theft deterrent.
The VTD part of the system disables the fuel injectors if someone attempts to start the vehicle with out the key.
The CTD system arms when you press the lock button on your remote twice....The horn should beep once when it has been armed.